US1812629A - Treatment of crude petroleum to prevent corrosion - Google Patents

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Patented June 30, 1931 UNITED .srAr s PATENT ac GHKRLE'S n. errr'onn, or Los ANGELES, CALIFORNIA, essienon, BY MESNE ASSIGN- MENTS, 'ro cauuon-rnurzrmn TREATING rnoonssns, turn, or .Los ensures, CALIFORNIA, A CORPORATION or CALIFORNIA TREATMENT CRUDE PETROLEUM TO PREVENT CORROSION ltis well known that certain varieties of crude oil, particularly such as are produced in the Gulf coastal plain, contain material quantities of sulfur in such chemical combination or condition that on standing or on heating they give off vapors which are highly corrosive to steel or iron, and particularly to thesteelof which stills, condensers and other refineryiequipment are composed.

It is also well known that many of these crudes, and particularly such as are high in sulfur, are produced from strata containing salt water or salt, and that such crudes often entrain material quantities of brine, which causes deposits of salt on metallic surfaces when heated to a temperature sufficient to drive off the water. 7

.It has heretofore been believed that these two phenomena were not connected, and efforts have heretofore been made to remove the sulfur from the crude prior to distillation, in order to 'prevent' the aforesaid corrosion, and to settle or wash the salt water from the oil to prevent incrustation.

1 have discovered that these two phenomena are directly connected and that the corrosion of metal parts which has heretofore been charged to the sulfur contained in the oil may, at least in many cases, be actually due to the breaking down of sodium chlorid :01" other water-soluble chlorids contained in the oil,'with the evolution of chlorin which, in the presence of steam, acts powerfully on ferrous metals and rapidly causes the destruction of equipment.

'I have further discovered that if substantially all 'of the salt or salts be removed from the oil prior to distillation this corrosion of equipment "will not take place, even when hydmgen sulfid is copiously evolved from the heated oil. This leads me to believe (though I do not know it to be true) that minute quantities of chlorin may act as a carrier, forming a ferrous chilorid which, in the'presence of heat, an excess of steam and an excess of hydrogen sulfid, is first converted to ferrous oxid with the regeneration of the chlori-n, the oxidthen reacting with hydrogen sulfi'd to form the sulfid of iron A Application filed May 28, 1928. .Serial No. 281,861.

of which the corrosion deposit appears to mainly consist.

Be that vas it may, I have ascertained that if the salt be removed the corrosion does not take place, even after long continued operation of the apparatus, and, of course, with the removal of the salt, incrustation is also avoided, a double purpose thus being served.

I have further discovered that in many if not most of the cases in which corrosion is severe, the salt contained in the oil is'not all in the form of brine, careful analysis show ing that the content of salt is much greater than can be dissolved in the quantity of water present in the oil. In such cases it has proven impossible to separate the salt by settling or other gravity-difference method, or even by washing the oil with hot water and settling. in some cases it has been possible, by means of long continued washing, to remove as much as eighty percent of the orig inal salt content, but this method does not appear to be commercially feasible, first, be cause corrosion is merely reduced and not eliminated thereby, and second, because the plosi1 of the washing process is prohibitively I have further discovered that the reason why washing and settling do not sufiice to remove all of the salt'is that the oil contains salt in microscopic grains, either dry or containing sufiicient water to render them moist but not sufficient to dissolve them, and that these grains (or perhaps only such of them as are moist) are coated with a skin which is repellant to water, for which reason these grains are notsubject to solution in water on the mere agitation of water with the oil.

I have further discovered that these grains may be stripped oftheir skins and the salt thus be rendered amenable to solution in water and to separation from the oil, in the manner about to be described.

I first build up a layer of finely pulverized mineral matter in an apparatus in which the oil may be forced through the layer, such as a filter press or a closed percolation tower to which pump or air'pressure may be applied. The mineral matter should be of a finely porous nature, should not be rendered muddy or slimy by wetting with water, and is most effective if it presents many rough or sharp surfaces or angles. I prefer diatomaceous or infusorial earth, calcined if possible, as

and pumping'the magma into the press, or'

by feeding the pulverized mineral in small proportions into the stream of oil entering the press during the progress of the treatment. The manner in which the cake is built up is no part of my invention, nor do I limit myself to any particular thickness of cake, as this will depend on the fineness of the mineral matter used and on its degree of porosity. In using diatomaceous earth it is possible to get good 7 results with cakes rangin from one-eighth inch to one inch in thickness, though I prefer to keep the thickness between say one-fourth and one-half inch, as this gives sufiicient depth for complete treatment without causing undue back pressure. Vith coarser and less porous materials such as fullers eartha much greater depth, up to several inches or even feet, maybe used to advantage.

I prepare the oil for treatment in the following manner. First, unless entirely fluid at atmospheric temperature I heat it to a temperature at which it is sufficient fluid to pass readily through the cake under a reason able pressure, for instance, from 100 to 120 Fahr. Second, if it contains any large proportion of emulsion, I first submit it to a demulsifying step, which is no part of my present invention and which may be conducted in any ordinary or preferred manneri A quantity of emulsion slightly greater than is permissible in the finished oil may be disregarded, as the final treatment usually has a slight demulsifying effect, though this is quite incidental and not an object of my invention. Third, if the oil carries too little water to dissolve the salts which it is known to contain, I introduce into the oil a small proportion of water (up to say five or six pounds of water per barrel of oil) in such manner that the water will be reduced to a state of very fine subdivision and thoroughly disseminated throughout the oil. The first or heating step and the step of adding water may be combined by heating the oil to the desired temperature by injection into it of low pressure wet steam, which will condense (particularly into a moving body or stream of oil) in a very desirable and favorable condition of subdivision and dissemination.

While the step of addition of water may be omitted in case the oil already contains enough water to dissolve the salt, the deter mination of salt is tedious and, as a small excess of water is not detrimental, I find it preferable to make the addition of water in almost every case.

The oil being thus prepared I pump or otherwise force it through the layer of pulverized mineral and obtain as an effluent an oil free from salt, but mixed with droplets of strong brine which, 011 standing, readily sep arate from the oil, leaving it dry and saltfree. The oil thus prepared may be stored or distilled with impunity, without danger to tanks in which it is stored or to apparatus in which it is distilled or in which its vapors are condensed. e

t should be observed that this simple treatment is neither a demulsification nor a filtration process. It is not demulsification, as the presence of much emulsion in the oil may or may not interfere with the desalting, and the emulsion may or may not be broken, the two functions thus appearing to be entirely independent and disconnected. For this reason it is prudent to demulsify (if demulsification is required at all) prior to the desalting treatment just described. It is not a simple filtration process because, first, there is no accumulation of emulsion or salt on the intake side of the cake, such as would ob-' viously result if the cake acted merely to strain out the salt granules, and second, because if insufficient water he used the entire cake may become choked with salt and become completely impenetrable in a short time, while if the proportion of water used is sufiicient the cake will remain open and permeable and treatment may be continued al most indefinitely.

What I believe actually happens is this: the salt granules are sufliciently small to enter the body of the cake of porous material, but in passing through the microscopic channels between the grains of such material, and through these grains if the material be of the order of porosity of diatomaceous earth, the salt- ,crystals are retarded and interrupted and are thus stripped of such skins of water repellant material as may surround the gran ules. At the same time they are subjected to contact with minute particles of Water (constantly passing through all parts of the cake because of the fine dissemination of thewater throughout the oil) and are thus brought into the condition of a strong solution or brine. This brine, having a stronger surface attraction than the oil for the min eral material of the cake, displaces the oil from the mineral grains and thus tends to accumulate into droplets which are carried through the cake by the oil pressure behind them as soon as they reach a sufiicient size to obstruct the channels in which they form.

In brief, the rationale of the process is to entrap the salt particles, hold them in a relatively fixed pO-SiLlOD, subject them to the fortime, but

cient to bring fluidity; adding to and intimately cible impact of water particles by which they are brought into solution, and finally eject the solution in the form of brine droplets of such dimensions as will spontaneously separate from the oil by sedimentation or other gravity effect.

If the water present in the oil when it enters the cake be materially less than the quantity required to bring the salt into solution, a partial or perhaps a complete separation of the salt will take place for a short as this salt remains in the cake the latter will soon be choked and the flow of liquid through it will cease, The feed of oil may then be interrupted and the cake washed free from salt by the passage of Water through it. This method of operating requires a constant reversal of feed, from oil to water and vice versa, introduces large excess quantities of water when washing through, and in general is not a desirable operating method from a commercial standpoint, though it falls entirely Within the purview of my invention.

I greatly prefer to carry out my process continuously: first demulsifying the oil, it demulsification is necessary, in a separate operation; then establishing a flow stream of the oil and continuously heating it by the injection of such quantity of steam as will introduce the desired proportion of water; passing the heated flow stream through the cake of pulverized materal, and finally separating the eiiiuent from the cake into an oil portion and a brine portion. This final step may be either continuous or intermittent as preferred. Conducted in this manner the process becomes ahnost entirely continuous, and need be stopped only to replace the cake with fresh material when choked with such entirely foreign matter as slimy clay which may accompany the water produced with the oil and which may not be entirely removed prior to the application of my process.

It will be understood that the results produced in this process follow from the simultaneous passage through the cake of salt-containing crude and a quantity of water suifithe salt or salts into solution, and that they will not be produced it the oil is passed through the cake prior to the addition of the water or if the water be added and thereafter removed (as by settling) prior to filtration. The desalting eflect herein obtained is a joint function of filtration in the presence of water and is not the sum of the functions of separate filtration and treatment with water.

I claim as my invention:

1. A method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: separating from said petroleum any excess quantity of emulsion; heating said petroleum to a temperature of disseminating throughout said petroleuma suflicient quantity of water to dissolve the'salt con-v tained therein; passing said petroleum and said added water through a layer of finely pulverized porous material, and separating the efflux from said layer into an oil portion and a brine portion. V 2. A method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: heating said petroleum substantially free from emulsion to a temperature of fluidity; adding to and intimately disseminating throughout said petroleum a sufficient quantity of water to dissolve the salt contained therein; passing said petroleum and said added Water through a layer of finely pulverized porous material, and separating the eiflux from said layer into an oil portion and a brine portion.

3. A method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: heating said petroleum to a temperature of fluidity; adding to and intimately disseminating throughout said petroleum less than six pounds of water per barrel of petroleum, said water being suificient in quantity to dissolve the salt contained therein; passing said petroleum and said added water through a layer of finely divided porous material, and separating the efliux from said layer into an oil portion and a brine portion by gravity difference.

4. A method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: adding to and intimately disseminating throughout said petroleum a quantity of water sufiicient to dissolve the salt contained therein; passing said petroleum and said added water through a layer of finely pulverized porous material, and separating the efliuX from said layer into an oil portion and a brine portion by gravity differonce.

5. A method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: passing said petroleum through a layer of finely pulverized porous material for separating said salt from said petroleum and simultaneously passing through said layer water not originally contained in said petroleum for removing said salt from said porous material.

6. A continuous method of rendering crude petroleum containing inorganic salts noncorrosive to metals, comprising: establishing a flow stream of said petroleum; injecting steam into said petroleum, thereby heating said petroleum to a temperature of fluidity and simultaneously adding water to said petroleum in quantity suflicient to dis- I solve the salt contained therein; passing said heated petroleum and said added water through a layer of finely pulverized porous material, and separating the efllux from said layer into an 011 portion and a brine portion.

7. A method substantiallyas set forth in claim 5 in Which'the layer is composed of fine- 1 1y divided diatomaceous earth.

8. A method substantially as setforthin claim 6 in which the layer is composed of fine- 5 i 7 1y divided dlatoniaoeous earth. In Witness that I claim the foregoing I have hereunto subscribed my name this 11th day of May,-192 8. e CHARLES D GIFFORD.